Anti-blocking method for acid gas pipeline of vacuum potassium carbonate desulfurization system

Abstract

The present application relates to the technical field of coal chemical industry, and particularly relates to a method for preventing blockage of an acid gas pipeline of a vacuum potassium carbonate desulfurization system, which comprises the following steps: step one, introducing steam into the acid gas pipeline to control the temperature in the acid gas pipeline to be greater than or equal to 50 DEG C; step two, using desulfurization rich liquid to flush the acid gas pipeline; and step three, after the steam and the desulfurization rich liquid are discharged from the acid gas pipeline and separated from the acid gas, the steam and the desulfurization rich liquid are sent into an ammonia stripping unit to produce concentrated ammonia water. The present application heats the inside of the acid gas pipeline by introducing steam into the acid gas pipeline, so that oily components cannot be condensed and precipitated, thereby preventing the acid gas pipeline from being blocked by the condensed oily components. The acid gas pipeline is flushed by using the desulfurization rich liquid, so that water-soluble salts are prevented from blocking the acid gas pipeline, the service life of the post-pump conveying pipeline of the vacuum pump in the desulfurization regeneration process is prolonged, and the cleaning cost and the safety risk in the cleaning process are reduced.

Description

Technical Field

[0001] This invention relates to the field of coal chemical technology, specifically to a method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system. Background Technology

[0002] Raw coal gas is dust-laden gas produced during the low-to-medium temperature pyrolysis of coal. Due to its complex composition, raw coal gas typically undergoes gas-liquid separation and is cooled to 19-21°C in a primary cooler. After electrostatic precipitator treatment, it is then sent to subsequent processing stages by a blower. Only after processes such as naphthalene washing, ammonia absorption, benzene washing, and desulfurization can it be effectively utilized as clean coal gas. Currently, desulfurization technologies used for benzene-washed coal gas mainly include dry desulfurization and wet desulfurization technologies. Wet desulfurization technologies further include wet catalytic oxidation and wet circulating absorption processes.

[0003] Vacuum potassium carbonate desulfurization is one of the widely used wet circulating absorption processes in China. It consists of two steps: absorption and regeneration. Using KOH solution as the alkali source, the potassium carbonate desulfurization liquid absorbs acidic gases such as H2S, HCN, and CO2 from the coal gas, becoming a rich liquid. This rich liquid is then heated and regenerated under vacuum conditions, releasing acidic gases that serve as raw materials for the sulfur recovery unit to produce sulfur with a purity ≥99.5%. The vacuum potassium carbonate desulfurization process utilizes the residual heat released from the cooling of raw coal gas in the primary cooler to release the acidic gases from the rich liquid under vacuum conditions. It offers advantages such as low acid gas regeneration temperature (only 58-63℃), high desulfurization efficiency, extremely slow side reaction rates, low waste liquid, low alkali consumption, and no need for a separate salt extraction system. However, because the regenerated acidic gas usually contains oil and salt, and it requires condensation and recovery, the acidic gas pipeline is prone to blockage, increasing maintenance costs and reducing production efficiency. Summary of the Invention

[0004] To address the technical problem of easy blockage in acid gas pipelines of vacuum potassium carbonate desulfurization systems, this invention provides a method for preventing blockage in acid gas pipelines of vacuum potassium carbonate desulfurization systems. This method involves heating the inside of the acid gas pipeline by introducing steam, preventing the condensation of oily components and thus preventing blockage. Furthermore, flushing the acid gas pipeline with desulfurization-rich solution avoids blockage by water-soluble salts, extends the service life of the downstream delivery pipeline of the vacuum pump in the desulfurization regeneration process, and reduces cleaning costs and safety risks during the cleaning process.

[0005] This invention provides a method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system, comprising the following steps:

[0006] Step 1: Introduce steam into the acid gas pipeline to control the temperature inside the acid gas pipeline to ≥50℃, prevent oily components from clogging the acid gas pipeline, and maintain the pressure inside the acid gas pipeline to ≥134kPa;

[0007] Step 2: Flush the acid gas pipeline with desulfurization rich solution to prevent water-soluble salts from clogging the acid gas pipeline;

[0008] Step 3: After steam and desulfurization rich liquid are discharged from the acid gas pipeline, they are separated from the acid gas and sent to the ammonia stripping unit to produce concentrated ammonia water.

[0009] Furthermore, the acid gas pipeline is the post-pump delivery pipeline of the vacuum pump in the vacuum potassium carbonate desulfurization system. Acid gas containing H2S, HCN, CO2, etc., is discharged from the top of the desulfurization regeneration tower, condenses and cools to room temperature, and then enters the pre-pump delivery pipeline of the vacuum pump. Because the pre-pump delivery pipeline is under negative pressure, oily components do not easily condense and precipitate, thus preventing blockage. However, when the acid gas enters the post-pump delivery pipeline, the pressure inside the post-pump delivery pipeline is greater than that inside the pre-pump delivery pipeline. This causes oily components to condense and precipitate in the post-pump delivery pipeline, leading to blockage and hindering the delivery of acid gas.

[0010] Furthermore, in step one, the oily components include naphthalene and benzene, and the water-soluble salts include ammonium salts and other metal salts.

[0011] Furthermore, in step two, the steam is saturated steam or superheated steam, preferably superheated steam. The saturated steam or superheated steam can be the steam used to heat the desulfurization regeneration tower in a vacuum potassium carbonate desulfurization system.

[0012] Furthermore, the steam pressure is ≥0.4MPa and the steam temperature is ≥150℃.

[0013] Furthermore, in step three, the rich desulfurization solution is the rich solution at the bottom of the desulfurization tower. Under the action of airflow in the vacuum pump and the post-pump delivery pipeline, this invention can use a small amount of rich desulfurization solution to flush the post-pump delivery pipeline of the vacuum pump over a large area, reducing pipeline cleaning costs without affecting the rich solution desulfurization regeneration. The rich desulfurization solution used to flush the post-pump delivery pipeline of the vacuum pump can also be recycled and reused.

[0014] Furthermore, in step three, the desulfurization rich liquor enters the acid gas pipeline through a stainless steel pipe connecting the rich liquor pump and the acid gas pipeline, and then flushes the acid gas pipeline. Branch pipes can be installed on the stainless steel pipe, allowing the desulfurization rich liquor to be sprayed into the acid gas pipeline from multiple locations simultaneously.

[0015] Furthermore, in step four, after the steam and desulfurized rich liquid are discharged from the acid gas pipeline, they are separated from the acid gas by the action of the water seal and the acid gas separator.

[0016] Furthermore, after the steam and desulfurization rich liquid are separated from the acid gas, they are condensed, allowed to stand, and separated to obtain an oil phase and an aqueous phase. The aqueous phase is sent to the ammonia stripping unit to produce concentrated ammonia water.

[0017] Furthermore, electric heat tracing equipment is installed on the acid gas pipeline for auxiliary heating.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention provides a method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system. Taking into full account the characteristics of the acid gas pipeline as a post-pump delivery pipeline, where naphthalene will directly transform from a gaseous state to a solid state below 50°C under post-pump pressure, forming flaky crystalline blockages that easily cause pipeline blockage, this invention introduces steam into the acid gas pipeline to control the temperature inside the pipeline to ≥50°C, preferably 50-60°C, to prevent oily components from condensing and precipitating under the higher pressure inside the acid gas pipeline. The acid gas pipeline is also flushed with desulfurization rich solution to prevent water-soluble salts from crystallizing or depositing inside the acid gas pipeline, thus preventing pipeline blockage. Simultaneously, this method enables the reuse of steam and desulfurization rich solution. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a process flow diagram for preventing blockage in the acid gas pipeline of the vacuum potassium carbonate desulfurization system in Example 1.

[0022] In the diagram, 1-desulfurization tower, 2-rich liquid pump, 3-centrifugal pump, 4-desulfurization regeneration tower, 5-reboiler, 6-upper section of acid gas condenser cooler, 7-lower section of acid gas condenser cooler, 8-acid gas cooler, 9-vacuum pump unit, 10-acid gas mist eliminator, 11-underground pool, 12-condensate pump, 13-acid gas separator, 14-acid water pump, 15-steam diversion pipe, 16-Claus furnace, 17-rich liquid diversion pipe, 18-acid gas pipeline. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0024] Example 1

[0025] like Figure 1As shown, the vacuum potassium carbonate desulfurization system involved in Example 1 includes a desulfurization tower 1. The bottom of the desulfurization tower 1 is connected to the inlet end of the rich solution pump 2. One outlet end of the rich solution pump 2 is connected to the top inlet end of the desulfurization regeneration tower 4. The other outlet end of the rich solution pump 2 is connected to the acid gas pipeline 18 through the rich solution diversion pipe 17. The inlet end of the acid gas pipeline 18 is connected to the outlet end of the vacuum pump unit 9. The outlet end of the acid gas pipeline 18 is connected to the inlet end of the acid gas demister 10. The two outlet ends of the acid gas demister 10 are respectively connected to the inlet end of the underground pool 11 and the inlet end of the acid gas separator 13. The outlet ends of the underground pool 11 and the acid gas separator 13 are respectively connected to the condensation section through the condensate pump 12 and the acid water pump 14. The other outlet end of the acid gas separator 13 is connected to the Claus furnace 16. Among them, the rich solution diversion pipe 17 is a D25×3mm stainless steel pipe.

[0026] The acid gas pipeline 18 is also connected to the steam inlet pipe 15. The bottom of the desulfurization regeneration tower 4 is connected to the top of the desulfurization tower 1 through the centrifugal pump 3. The bottom of the desulfurization regeneration tower 4 is also connected to the reboiler 5. The reboiler 5 transfers heat with the desulfurization liquid discharged from the desulfurization regeneration tower 4. The top outlet of the desulfurization regeneration tower 4 is connected to the vacuum pump unit 9 in sequence through the upper section 6 of the acid gas condenser cooler, the lower section 7 of the acid gas condenser cooler, and the acid gas cooler 8.

[0027] A method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system includes the following steps:

[0028] Step 1: Divide the blockage sample into two equal portions, labeled Sample A and Sample B respectively. Extract the oily components from Sample A and Sample B using toluene and tetrahydrofuran, respectively, and extract the water-soluble salts from Sample A and Sample B using water. After extraction, determine the components and mass percentages of the extracts from Sample A and Sample B, and calculate the average value of each component. The results are shown in Table 1. The blockage sample was taken from the acid gas pipeline 18 after the vacuum pump unit 9 in the vacuum potassium carbonate desulfurization system. The blockage sample was ground before extraction.

[0029] Table 1. Composition and mass percentage of acid gas pipeline blockage samples

[0030]

[0031] Table 1 shows that in the blockage within the acid gas pipeline 18 after the vacuum pump unit 9, the average mass percentage of oily components was 53.6%, the average mass percentage of total water-soluble salts was 8.56%, and the average mass percentage of insoluble residue was 33.09%. The sum of the average mass percentages of oily components and water-soluble salts in the blockage was significantly greater than the average mass percentage of insoluble residue, indicating that the blockage was mainly caused by the high total content of oily components and water-soluble salts in the gas. Since the oily components in the gas are mainly benzene and naphthalene, and benzene oily components are not easily condensed and precipitated, the oily components in the blockage were mainly naphthalene. Among the water-soluble salts, total ammonia includes fixed ammonia and volatile ammonia.

[0032] Step 2: Superheated steam is introduced into the acid gas pipeline 18 through the steam inlet pipe 15, controlling the temperature inside the acid gas pipeline 18 to 50-60℃ to prevent oily components from clogging the acid gas pipeline 18. The pressure of the superheated steam is ≥0.4MPa, and the temperature of the superheated steam is ≥160℃. After the acid gas passes through the upper section 6, the lower section 7, and the acid gas cooler 8 in sequence, its temperature drops to 25℃. Under the action of the vacuum pump unit 9, the pressure inside the acid gas pipeline at the front end of the vacuum pump unit 9 (i.e., the inlet end of the vacuum pump unit 9) is -84KPa. At this point, naphthalene has not reached saturation and will not condense to cause blockage. The relationship between the saturated vapor pressure P (mmHg) and temperature T (°C) of naphthalene is: LgP = 5.8099 - 978.66 ÷ (T + 118.39). From this, the saturated vapor pressures of naphthalene at 25°C and 50°C can be calculated to be 0.01287 kPa and 0.1093 kPa, respectively. It is evident that the saturated vapor pressure of naphthalene at 50°C is 8.49 times that at 25°C. The pressure in the acid gas pipeline 18 at the rear end of vacuum pump unit 9 (i.e., the outlet end of vacuum pump unit 9) is 134 kPa, which is 7.73 times the pressure in the acid gas pipeline at the front end of vacuum pump unit 9. Therefore, heating the acid gas in the acid gas pipeline 18 at the rear end of vacuum pump unit 9 to above 50°C will ensure that naphthalene does not condense from the acid gas. To ensure that the temperature inside the acid gas pipeline 18 is not lower than 50°C, in this embodiment, an electric heat tracing device is installed on the outside of the acid gas pipeline 18 between the rear end of the vacuum pump unit 9 and the acid gas separator 13 for auxiliary heating. The heating temperature of the electric heat tracing device is set to 50-60°C.

[0033] Step 3: Use the rich liquid pump 2 to spray and flush the rich liquid at the bottom of the desulfurization tower into the acid gas pipeline 18 to prevent ammonium bicarbonate from clogging the acid gas pipeline 18.

[0034] Step 4: After the steam and desulfurization rich liquid are discharged from the acid gas pipeline 18, they are separated from the acid gas by the action of the water seal and the acid gas separator 13. The separated liquid phase is sent to the condensation section by the acid water pump 14. After settling and separation, the oil phase and water phase are obtained. The water phase is sent to the ammonia stripping unit to produce concentrated ammonia water.

[0035] The temperature of the Claus furnace 16 was tested and the cleaning frequency of the acid gas pipeline in the vacuum potassium carbonate desulfurization system was monitored. In this embodiment, the temperature of the Claus furnace 16 was 1240-1260℃. Compared with the vacuum potassium carbonate desulfurization system without the anti-clogging method provided by this invention, the temperature of the Claus furnace 16 only decreased by 10-20℃, which can meet the requirements for normal production of the Claus furnace. The cleaning frequency of the acid gas pipeline was once every six months. In the vacuum potassium carbonate desulfurization system without the anti-clogging method provided by this invention, the cleaning frequency of the acid gas pipeline was once every 1-2 months. This shows that the anti-clogging method provided by this invention can effectively extend the service life of the pump post-pump delivery pipeline in the desulfurization regeneration process.

[0036] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system, characterized in that, Includes the following steps: Step 1: Introduce steam into the acid gas pipeline to control the temperature inside the acid gas pipeline to ≥50℃, prevent oily components from clogging the acid gas pipeline, and maintain the pressure inside the acid gas pipeline to ≥134kPa; Step 2: Flush the acid gas pipeline with desulfurization rich solution to prevent water-soluble salts from clogging the acid gas pipeline; Step 3: After steam and desulfurization rich liquid are discharged from the acid gas pipeline, they are separated from the acid gas and sent to the ammonia stripping unit to produce concentrated ammonia water; The acid gas pipeline is the downstream delivery pipeline of the vacuum pump in the vacuum potassium carbonate desulfurization system. The steam pressure is ≥0.4MPa and the steam temperature is ≥150℃.

2. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, The oily components include naphthalene and benzene, and the water-soluble salts include ammonium salts.

3. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, The steam is either saturated steam or superheated steam.

4. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, The rich desulfurization solution is the rich solution at the bottom of the desulfurization tower.

5. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, The desulfurized rich liquor enters the acid gas pipeline through a stainless steel pipe that connects the rich liquor pump and the acid gas pipeline, and then flushes the acid gas pipeline.

6. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, After steam condensate and desulfurization rich liquid are discharged from the acid gas pipeline, they are separated from the acid gas by the action of water seal and acid gas separator.

7. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, After the steam and desulfurization rich liquid are separated from the acid gas, they are condensed, allowed to stand, and separated to obtain an oil phase and an aqueous phase. The aqueous phase is sent to the ammonia stripping unit to produce concentrated ammonia water.

8. The method for preventing blockage in the acid gas pipeline of a vacuum potassium carbonate desulfurization system as described in claim 1, characterized in that, Electric heat tracing equipment is installed on acid gas pipelines for auxiliary heating.

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